1. Field of the Invention
The present invention relates to the formation of boride barrier layers and, more particularly to boride barrier layers formed using chemisorption techniques.
2. Description of the Related Art
In the manufacture of integrated circuits, barrier layers are often used to inhibit the diffusion of metals and other impurities into regions underlying such barrier layers. These underlying regions may include transistor gates, capacitor dielectric, semiconductor substrates, metal lines, as well as many other structures that appear in integrated circuits.
For the current subhalf-micron (0.5 μm) generation of semiconductor devices, any microscopic reaction at an interface between interconnection layers can cause degradation of the resulting integrated circuits (e.g., increase the resistivity of the interconnection layers). Consequently, barrier layers have become a critical component for improving the reliability of interconnect metallization schemes.
Compounds of refractory metals such as, for example, nitrides, borides, and carbides have been suggested as diffusion barriers because of their chemical inertness and low resistivity (e.g., resistivity typically less than about 200 μΩ-cm). In particular, borides such as, for example, titanium diboride (TiB2) have been suggested for use as a barrier material since layers formed thereof generally have low resistivity (e.g., resistivity less than about 150 μΩ-cm).
Boride barrier layers are typically formed using chemical vapor deposition (CVD) techniques. For example, titanium tetrachloride (TiCl4) may be reacted with diborane (B2H6) to form titanium diboride (TiB2) using CVD. However, when Cl-based chemistries are used to form boride barrier layers, reliability problems can occur. In particular, boride layers formed using CVD chlorine-based chemistries typically have a high chlorine (Cl) content (e.g., chlorine content greater than about 3%). A high chlorine content is undesirable because the chlorine may migrate from the boride barrier layer into adjacent interconnection layers, which can increase the contact resistance of such interconnection layers and potentially change the characteristics of integrated circuits made therefrom.
Therefore, a need exists in the art for reliable boride barrier layers for integrated circuit fabrication. Particularly desirable would be reliable boride barrier layers useful for interconnect structures.